On my pre-run check of my model I noticed that the Pipe Density and Fluid Density of all the elements I designated as buried have been set to 0.0. I guess weight is factored into the mesh?

Thanks,
Levi

When you analyze buried piping you're interested in thermal strain. Also your buried pipe is a continuous beam on an elastic foundation. As such, there are no weight stresses (assuming the soil properly supports the pipe). The only way to achieve this in CAESAR II is to assume the densities are zero.

Richard if the density is 0, it means there is not settlement. it would not be better consider density? and so the software could calculate the settlement.

On the other hand if the density is 0, it means i cannot put earthquake.

How i can solve in caesar this settlement by weight and the earthquake case?

The pipeline codes are interested in thermal strain. These codes don't address settlement. If this is what you're after you will need a full fledged FEA program that can mesh not just the pipe, but the soil too.

For a seismic event, either the pipe moves with the soil (so no induced load /stress), or you cross a fault line, in which case the pipe breaks, or at best yields. Pipe Flexibility programs do not adequately address either situation.

Adding density would result in an unrealistic deflection of the pipe.The various springs would be identical to rack supports, with a catenary between each of them.

If you need to analyze what underground settlement will do, you need to calculate the deflected shape of the pipe and move it to that configuration via displacements.

However, any soils science you apply to your pipe will be influenced with large levels of subjectivity.

Well,
I am thinking in settlement between underground pipe and above pipe, in my opinión in this área this issue is very important.

thanks

We agree, however, settlement isn't an output. It's an input.

Do this:
1) Model your system ignoring deflection. Apply additional reference nodes as needed for step 2.
2) take a copy of your system and eliminate everything beyond the second support above ground and everything beyond the first bend plus some token distance. Apply deflections from the model in step 1 at the end points. (You are effectively applying a value judgement as to which part of the pipe will move/stress due to settlement.)
3) Instead of settling and moving the underground pipe, move the above ground pipe in the opposite direction at the support points and end point.
4) If attempting to meet a specific settlement, update models 1 and 2 in a cyclical pattern until you meet your desired displacement.

Note, this differs from analyzing settlement of equipment and supports because the underground section of the pipe is relatively difficult to instruct to settle.

If we have the soil characteristics, and we have the weight of the pipe. Why not calcualte the settlement in the software (obviously i can always calculate this and see how to enter it)

In others piping software do it

On the other hand (Richard) , i don´t agree with you afirmation "The pipeline codes are interested in thermal strain. " in my opinión the codes are intereseted in strain, not necessary thermal strain.

I believe we have confusion on what settlement is defined as.

Settlement, as far as pipe is concerned, is the plastic deformation of the soils over time.

The expectation by the stress analyst, engineering consultant, and authors of CAESAR and its buried piping module is that the individuals burying the pipe are taking the effort to prepare the soil under the pipe, compacting it so that it is at the elevation specified on the fabrication drawing. The same is said about the soil around and on top of the pipe.

By plugging density back in, you will have unrealistic results. Piping will be seen as sagging in the middle, when if anything, piping has a tendency to erupt out of the ground upwards when not properly designed.

Well
The soil may be very well compacted, but that will not prevent some soil stiffness, and that soil stiffnes affected by loads of weight will produce some settlement.
Other thing, (maybe more interesting) is the "upheaval buckling" and the posibility the pipe erupt out of the ground. (see K Petér´s Method).

But the settlement give loads (in conections) and stress in my pipe, and in GRP pipe it could be important. Why not use the sustained load, why ignore the density?

Agreed. The soil has stiffness, and at the end of day 1 when the fabricators are complete, the pipe will not perfectly align with the AutoCAD model that demonstrates perfect straightness. However, we generally accept that the piping code has robustness built into it as a result of statistically-driven data to account for small deviations.

If you expect significant sagging in your soil, then I see three options to do this within CAESAR:
1) Keep the pipe and fluid densities intact and adjust the springs to account for this weight to achieve the sag level you are expecting.
2) Keep the springs constant and adjust the pipe and fluid densities upwards until you achieve the result you want.
3) Manually displace nodes in CAESAR to get your configuration.

I think for the software to be updated to automatically handle what you want, there will need to be a published work that accurately describes the phenomenon you wish to achieve.